The present invention relates to improvements in electrostatic copying machines of the type wherein the image of an original is transferred onto a photosensitive layer and is thereupon developed with a pulverulent or liquid developing agent prior to being transferred onto a preferably sheet-like copy carrier. The photosensitive layer of an electrostatic copying machine is often applied to the periphery of a rotary copying drum. The drum must be inspected, repaired or replaced at certain intervals. In presently known copying machines, the removal of that component which is provided with the photosensitive layer is a tedious and time-consuming task because the component must be mounted in a predetermined position with a high degree of accuracy in order to insure proper imaging of originals, development of images and transfer of developed images onto a copy carrier. Such work must be performed by skilled persons and invariably necessitates lengthy interruptions in operation of the copying machine. Additional problems arise in connection with cleaning of the aforementioned component for the purpose of removing from the photosensitive layer remnants of a pulverulent or liquid developing agent. Such remnants accumulate in the housing and must be removed from time to time in order to reduce the likelihood of contamination of the machine and/or of the surrounding area (if the developing agent includes solid toner particles). The parts of the cleaning unit undergo considerable wear so that they must be replaced at rather frequent intervals. In many instances, the wear upon the parts of the cleaning unit for the photosensitive layer progresses at the same rate as the wear upon the component which is provided with the photosensitive layer. The parts which clean the photosensitive layer may constitute or include rotary brushes, endless bands, bands of finite length or the like.
It was already proposed to assemble the parts of the cleaning unit for the photosensitive layer in an electrostatic copying machine into a self-sustaining module which can be inserted into and removed from the housing of the copying machine with little loss in time. Reference may be had to commonly owned U.S. Pat. No. 3,672,764 granted June 27, 1972 to Hartwig et al. Such modular construction of the cleaning unit contributes to simplicity of the copying machine and reduces the intervals of idleness; however, the removal of a defective component which is provided with a photosensitive layer or the mounting of a new component in the housing of a conventional copying machine is still a tedious and time-consuming task so that the modular construction of the cleaning unit cannot be used to full advantage, especially if the cleaning unit must be removed simultaneously with the aforementioned component (e.g., a rotary copying drum).